Wear-resistant metal alloy



Patented Feb. 14, 1939 UiTED STATES PATENT OFFICE No Drawing.Application July 21, 1937, Serial No. 154,862

4 Claims. (Cl. 75136) This invention relates to wear resistant metalcomposition, the object being to secure a metal suitable for the makingof the various types of wear resistant parts such as lathe centers, plugauges, burnishing tips, internal gauges, ring gauges, rest plates andother various elements .or devices utilized in a position subject toconsiderable wear and by such wear resistant metal secure long life inthe machines or devices equipped therewith or formed thereof.

The purpose of the invention therefore is to secure a very compact and ahighly wear resistant metal comprising an alloy of several metals thatis capable of taking a high polish to provide a glass-smooth wearingsurface. Of such hardness as not to be readily marred or worn throughfrictional contact with any of the usual metals employed in themanufacture of the various parts as, for instance and not by way oflimitation,

a vanadium steel shaft rotatable on a lathe or grinding machine centerformed of my improved wear resistant alloy.

In the manufacture of machine tools and the various parts oftheautomobile and other machines and devices, the metals utilized as themachine art has developed are being made of higher grade materials andusually of a greater hardness. To keep pace with this development, amaterially higher grade of wear resistant material is required. Forinstance, the centers in lathes for the turning of high grade steelelements are rapidly worn away and thus are of short life requiringconstant replacement. Also, plug gauges as another instance need to bevery accurate and if made of metals heretofore utilized are readily wornand soon become inaccurate requiring replacement.

This invention therefore seeks to provide a composite metal of acharacter of composition and method of manufacture thereof to secure awear resistant metal of improved. characteristics.

These and various other objects and features of the invention arehereinafter more fully described and claimed.

My improved wear resistant metal is composed of the following elementsalloyed togethernamely, tungsten carbide, nickel, molybdenum andchromium in the proportions hereinafter stated.

V The function of each of the elements of the composition is as follows:

The tungsten carbide containing 6 per cent carbon is the base metal andproduces the desired hardness and resistance to wear.

Nickel is used as a binding element inasmuch as the temperature at whichthe metal is formed liquefies the nickel which alloys with the tungstencarbide.

The molybdenum provides toughness and desired tensile strength and formsa ternary alloy 5 with the nickel and tungsten.

The chromium is utilized as a de-oxidizer.

The above enumerated elements are the essential elements of my improvedwear resistant metal but it is pointed out that a small propor- 10 tionof other elements or components may be utilized such as boron, silicon,tantalum, antimony, manganese, titanium, vanadium or zirconium. Eitherone or the other of these may be added to the base composition to securecerl5 tain additive characteristics as for instance, an increasedhardness and/or density.

The proportion of the base metals may vary inasmuch as there are manyplaces of use where an extreme hardness is not desirable and a com- 2(position for use where a lesser hardness is required and thus thepercentages of the metals -may be varied to produce articles ofdiflerent degrees of hardness and wear resistance.

As an example of the possible variation in the 24 percentages of thebase metals, I herewith give the preferred percentages of metals fromthe least hardness to the greater hardness.

' HARD HARDER HARDES'I -20 mza: -15 mia: -10 mix WC '77'.0% WC g 81.7%WC 86.5% Ni 19.2% Ni 14.4% Ni 9.6% Mo 2.8% Mo 2.9% Mo 2.9% Cr 1.0% Cr1.0% Cr .1.0% 35 The elements in any of the suggested percentages arefirst reduced to a very fine powder and thoroughly mixed by ball millingfor a period of from eighty to one hundred and twenty hours or moreuntil the composition is of such a fine- 40 ness as to pass a 400 meshscreen. The ball milling is to be performed in an atmosphere free fromoxygen and moisture. The powdered material is then placed in a mold andtamped and then submitted in the furnace to reducing at- 45 mosphere fora period of one to four hours, depending largely upon the size andnature of the piece to be formed. In order that the mass may be .ofuniform density and free from voids, the material is then placed in aresistance type of 50 furnace such for instance as is shown in my Patent2,074,038, granted Mar. 16, 1937, in which there is a plunger that mayenter the mold to engagement with the material and in which the cruciblelies between the electrodes of the fur- 55 nace. A lever is utilized tooperate the temp and a. gauge for indicating the pressures (not hereshown). The material under pressure of the tamp is submitted to heat,the pressure then reduced and the material allowed to cool and thisheating under pressure and cooling is best performed in a series ofsteps in which the pressure is increased step by step from an initialpressure of approximately 10,000 pounds to a flnalpressure of about20,000 pounds per square inch and in which the temperature is increasedstep by step from 900 degrees C. to in the neighborhood of 1750 degreesC.

The material is submitted to heat and pressure increased in degree ateach step and cooled therebetween and is important in that in theinitial step, the air and gas formed through the heating of the materialare gradually driven off so that at least in the final step if notbefore, the material is practically entirely freed from the gases andeven minute voids are prevented. The interval of cooling is not soimportant as to temperature change as it is to provide time intervalpermitting the gases to escape and the temperature drop is usually lessthan 200 degrees F. The time interval required for such drop intemperature is suflicient to permit the gases to discharge prior to thefinal step. The small percentage of chromium is included as one of thebase materials, its purpose being to free the materials 01' oxygen.Also, in the original steps, the material is not at alloying temperatureand is porous and by cooling between the successive applications of heatand pressure gives opportunity for development of the gases within thebody which in subsequent steps are eliminated from the material by thepressures and thus at the final temperature of 1350 to 1750 degrees 0.,at which the metals will alloy, there is no air, gas or oxygen presentin the body of the material or that will develop therein under thealloying temperature. It is these steps of the heating under pressureand cooling in succession that are productive of greater density of themass and as the principal ingredients, tungsten, nickel and molybdenumform a ternary alloy, I secure a metal that is not only of an extremehardness but one that will take a high polish and provides a metal thatis toan unusual degree wear resistant adapting it for the various usesas hereinbefore mentioned.

It will also be observed from the preceding list of possiblecompositions that a considerable variation may be made in thepercentages of the materials-that is, the amount. of tungsten may varyfrom approximately '76 to 8'7 per cent, the nickel=being of about 20 percent for the lower amount of tungsten and correspondingly decreasing toabout 9 per cent for the higher amount of tungsten while the molybdenumand chromium may be practically constant throughout the range oftungsten or nickel percentages. It is therefore to be noted that thenickel decreases in percentage as the tungsten is increased and therange in percentage of the tungsten and nickel given will provide a wearresistant metal of the desired properties of hardness and wearresistance as may be required for a specific use. The metal in any ofthe precentages given has practically thesame density and varies only inhardness. It is also capable of taking a very high polish so that themetal is useable as a light reflecting surface. The metal is consideredpractically black but, due to the ingredients, is more properlydescribed asa dark grey. It has a metal sheen and due to the finenessand density, a polished surface is capable of reflecting light withoutdistortion.

As previously suggested, additional elements such as boron, silicon,antimony and the like may be used to secure a somewhat greater hardnessand compactness or density and the percentages of such additive elementsmay be as high as 10 per cent of the total volume.

Elements such as boron, vanadium and the like have a tendency toincrease the hardness and antimony, for instance, has a tendency toproduce a greater density and in the event any such elements areutilized in the compositions as set forth in the preceding tables, acorrespondingly less percentage of tungsten and a slightly less,

metal of the iron group, such as cobalt, may be.

utilized and an additive element such as antimony may be used as suchelement tends to lower the temperature at which the metals will alloy.

Having thus fully described my invention, its utility and mode ofoperation, what I claim and desire to secure by Letters'Patent of theUnited States is 1. A wear resistant metal comprising the followingcompositions in percentages by weight to total per centnamely, atungsten carbide containing approximately 6 per cent carbon within therange of 76 to 87 per cent, nickel within the range of approximately 20per cent to 9 per cent, molybdenum-approximately 2.8 per cent, andchromium-approximately 1 per cent, the molybdenum and chromium beingpractically constant in percentage throughout the entire range ofpercentages of tungsten carbide and raced, alloy free from voids andhaving a glass smooth surface.

3. A wear resistant metal alloy comprising the following ingredients inpercentages by weight to total 100 per centnamely, a 6 per cent tungstencarbide within the range of approximately 76 to 87 per cent, nickelcorrespondingly within the range of 20 to 9 per cent, molybdenum 2.8 percent, chromium approximately 1 per cent, a small percentage of titaniumfor increasing hardness, and a small percentage of antimony having thecharacteristic of lowering the temperature at which the mass will alloy.

4. A wear resistant metal alloy comprising the following ingredients inpercentages by weight to total 100 per centnamely, a 6 per cent tungstencarbide within the range of approximately 76 to 87 per cent, a nickelcorrespondingly within the range of 20 to 9 per cent, molybdenum 2.8 percent, chromium approximately 1 per cent, and titanium up to 10 per cent.

FAY H. WILLEY.

